One-way clutch with cage-displacement limiting mechanism

ABSTRACT

A one-way clutch with a cage-displacement limiting mechanism is constructed of an outer race; an inner race concentric with the outer race; sprags arranged within a space between the outer and inner races and being displaceable between first positions, where the sprags are maintained in contact with the inner and outer races to transmit a torque, and second positions where the sprags cannot transmit any torque; first and second annular cages arranged within the space with a radial interval therebetween, holding the sprags in place, and being rotatable relative to each other between first relative positions, where the sprags are caused to move to the first positions, and second relative positions where the sprags are caused to move to the second positions; and a limiting member for connecting the cages to each other and for limiting the degrees of relative movements of the cages.

BACKGROUND OF THE INVENTION

(1.) Field of the Invention

This invention relates to a one-way clutch and more specifically to aone-way clutch with a cage-displacement limiting mechanism.

(2.) Description of the Prior Art

Typical conventional one-way clutches (hereinafter called "OWC") aresprag-type OWCs equipped with double cages, namely, both inner and outercages. In a sprag-type OWC, the inner and outer cages serve to arrangeplural sprags with equal angular intervals and to have all the spragsmove in unison. The structures and functions of conventional sprag-typeOWCs will hereinafter be described in brief with reference to FIGS. 9and 10.

FIG. 9 is a fragmentary cross-sectional view of a sprag-type OWC havingdouble cages. A flange 5a of an outer cage 5 is guided by an innerperipheral surface 1a of an outer race 1, while a flange 7a of an innercage 7 is guided by an outer peripheral surface 3a of the inner race 3.All sprags 11 can be brought into simultaneous engagement with the outercage 5 and inner cage 7 to bear each torque evenly, because the sprags11 are allowed to move relative to movements of the outer and innerraces 1,3. In the illustrated example, a ribbon spring 9 is interposedbetween the outer and inner cages 5,7 so that the sprags 11 are normallymaintained in contact with the inner and outer peripheral surfaces1a,3a. In FIG. 10, the flange 5a of the outer cage 5 is positioned at astepped portion of the outer race 1, where the flange 5a is supported bya support member 13. Further, the flange 7a of the inner cage 7 extendstoward the inner peripheral surface 1a of the outer race 1.

In the above-described conventional sprag-type OWCs each of which isequipped with the double cages, the so-called full phasing effect isknown to take place when the sprags are moved from their free positionsto their torque-transmitting locked positions. It is hence possible toachieve smooth transmission of torques even somewhat severe useconditions.

The above-described prior art is however accompanied by variousproblems. When such a conventional OWC is subjected to an excess torque,its sprags are caused to rise from their normal free positions and thento fall in the opposite direction beyond the cam height, in other words,to undergo the so-called rollover. As secondary outcomes, the cages aredeformed or broken and the ribbon spring are caused to undergo fatiguedue to its deformation. In addition, deep impressions are formed in bothinner and outer races, thereby making them no longer usable. In somesevere instances, the sprags cut into the outer and inner peripheralsurfaces of the inner and outer races and are no longer allowed to idle.

If the sprags undergo slipping and are hence unloaded while they aremaintained in engagement with the outer and inner peripheral surfaces ofthe inner and outer races, the sprags are immediately caused to falltoward the free side as a counteraction to the release of the load, inother words, the so-called popping phenomenon develops. The sprags thusstart stepping and hopping in a very short period of time. As a result,the sprags collide severely against the inter-pocket parts of the cagesand the cages are hence worn and deformed. In some worst cases, thesprags may move beyond their associated inter-pocket parts and enterforcibly between both cages. This phenomenon is called "pop-out". Whenthe sprags undergo popping, skid marks are formed on the inner camsurfaces of the sprags and the inner cam surfaces are therefore wornout, leading to wearing and breakage of the interpocket parts of thecages, deformation and breakage of the ribbon spring, etc. Even if onlyone of the sprags pops out, the inner cage is turned toward the idlingside by the pop-out and the other sprags are hence tilted toward thefree side and are thus separated from the outer peripheral surface ofthe inner race. As a consequence, the OWC loses its function as an OWCand can no longer transmit torques.

As typified by the above-described two examples, it is the falling ofsprags that causes serious problems in sprag-type OWCs. An OWC cannotfunction properly when its sprags fall excessively not only toward thefree side but also toward locked side.

In order to solve the above-described problems, it is indispensable toperform very strictly the control of the designing of the outerconfigurations of the sprags including their strut angles and thecontrol of the dimensional accuracy of the pockets of the inner cage. Itmay also be contemplated to increase the thickness of the inner cageand/or the torque capacity of the OWC so as to increase the safetyfactor. It may also be necessary to improve the material of the ribbonspring so as to make it more flexible.

If one tries to solve the above problems in the aforementioned manner,secondary problems arise such that the device becomes more complex inthat its manufacturing cost increases substantially due to the need forstrict designing and control of the dimensions of various parts, and theassembly work becomes difficult. Therefore, the above-mentioned solutioncannot be fully considered as a breakthrough and practical solution.

SUMMARY OF THE INVENTION

An object of this invention is to solve the above-mentioned problems ofthe prior art and hence to provide a one-way clutch which can readilymaterialize a structure capable of preventing the falling of sprags andensuring stable and smooth transmission of torques without need forincreased machining accuracy of various parts is economical and givesgood design margin or flexibility.

In one aspect of this invention, there is thus provided a one-way clutchwith a cage-displacement limiting mechanism, which comprises:

an outer race having an inner peripheral surface;

an inner race having an outer peripheral surface and arrangedconcentrically with the outer race;

sprags arranged within an annular space formed between the outer andinner races and being displaceable between first positions, where thesprags are maintained in contact with the inner and outer peripheralsurfaces to transmit a torque, and second positions where the sprags areunable to transmit any torque;

first and second annular cages arranged within the space with a radialinterval therebetween, holding the sprags in place, and being rotatablerelative to each other between first relative positions, where thesprags are caused to move to the first positions, and second relativepositions where the sprags are caused to move to the second positions;

a limiting means for connecting the cages to each other and limiting thedegrees of relative movements of the cages; and

a means for urging the sprags to the first positions.

The one-way clutch of this invention has inter alia the followingadvantages.

(1) Conventional OWCs required very high machining accuracy as to thedesigning of pockets and other parts. The present invention can easethis requirement. Namely, this invention gives better design flexibilityand facilitates the manufacturing.

(2) Although the relative displacement between an inner cage and itscorresponding outer cage has been limited by parts of pockets of theinner cage, it can be firmly limited by the entire pockets so that it isstabilized.

(3) Owing to the stabilized relative displacement, the wear of thepockets is reduced and the flexibility of the ribbon spring can be setat a lower degree. It is hence expected to show better performance undersevere conditions such as vibrations.

(4) As an outcome of the above advantages (1), (2) and (3), a highdegree of freedom is provided regarding the machining accuracy ofvarious parts and the selection of materials (especially, materials forthe sprags and ribbon spring) so that the manufacturing cost can belowered.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of this inventionwill become apparent from the following description and the appendedclaimed, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a fragmentary cross-sectional view of an OWC according to thefirst embodiment of this invention;

FIG. 2 is a fragmentary cross-sectional view of a modification of thefirst embodiment;

FIG. 3 is a fragmentary plan view of the OWC of FIG. 1 and shows spragsin their normal free positions;

FIG. 4 is similar to FIG. 3 but shows the sprags in their freepositions;

FIG. 5 is similar to to FIG. 4 but shows the sprags in their lockedpositions;

FIG. 6 is a fragmentary cross-sectional view of an OWC according to thesecond embodiment of this invention;

FIG. 7 a fragmentary cross-sectional view of a modification of the OWCof FIG. 6;

FIG. 8 is a fragmentary plan view of the OWC of FIG. 6; and

FIGS. 9 and 10 are fragmentary cross-sectional views of the conventionalOWCs.

In all the above figures, like elements of structure are identified bylike reference numerals.

The first embodiment will be described first of all. Referring to FIG.1, the OWC is constructed of the plural sprags 11 in the form of apeanut shell, the outer cage 5 and inner cage 7 of an annular shape, andthe ribbon spring 9. The sprags 11 are arranged side by side at equalangular intervals between the ring-shaped outer race 1, which has theinner peripheral surface 1a, and the ring-shaped inner race 3 which hasthe outer peripheral surface 3a opposing concentrically to the innerperipheral surface 1a. The sprags 11 serve to transmit torques. Theouter and inner cages 5,7 hold the sprags 11 therebetween. The ribbonspring 9 assembled between the outer and inner cages 5,7 serves toalways maintain the sprags 11 in contact with the inner and outerperipheral surfaces 1a,3a.

The outer and inner cages 5,7 respectively have annular flanges 5a,7awhich extend out radially, in opposite directions to each other, andsubstantially at right angles from one side surfaces thereof. Freeperipheral edge portions of the flanges 5a,7a are guided respectively bythe inner and outer peripheral surfaces 1a,3a. A rectangular shallownotch 5b (see, FIG. 3) is formed in the other side surface of the outercage 5. This notch 5b is provided at one location. If necessary, pluralnotches may be provided with equal angular intervals. On the other hand,an annular flange 7b is provided on the other side surface of the innercage 7. The annular flange 7b extends radially, substantially at a rightangle, toward the outer race 1. A part of the flange 7b also has anextension 7d (see, FIG. 3) extending toward the inner peripheral surface1a of the outer race 1 and having a rectangular shape in a plan. Thenumber of extensions 7d corresponds to the number of notches 5b.Further, the free peripheral end surface of the extension 7d has thesame radius curvature as the inner peripheral surface 1a of the outerrace 1 and is guided by the inner peripheral surface 1a.

As illustrated in FIG. 1, the extension 7d enters the notch 5b to forman engaged part. The axial depth (height) of the notch 5b is somewhatgreater than the thickness of the inner cage 7, namely, the extension7d. They are therefore maintained in mutual engagement with a sufficientclearance in the axial direction. Accordingly, they are not readilydisengaged even when vibrations are applied to the OWC.

Referring now to FIG. 3, X indicates a cross-section seen in thedirection indicated by arrows A,A' in FIG. 1. The sprags 11 are arrangedwith equal angular intervals. Both end portions of the sprags 11 areheld in pockets 5c of the outer cage 5 and in pockets 7c of the innercage 7 respectively. On the other hand, Y is a cross-section seen in thedirection indicated by arrows B,B' in FIG. 1 and shows the manner ofengagement between the notch 5b and extension 7d. As is understood fromY of FIG. 3, the peripheral length of a notch 5b of the outer cage 5 isgreater than the peripheral length of an extension 7d of the inner cage7. Accordingly, a suitable degree of clearance is formed at the engagedparts of the outer and inner cage 5,7. Owing to the provision of theclearance, the outer and inner cages 5,7 are allowed to move relative toeach other within a range not deleteriously affecting the performance ofthe OWC. This clearance is set at such a degree that the vibrations ofthe sprag 11 are not limited beyond necessity.

The operation of the OWC according to the first embodiment of thisinvention, which OWC is equipped with the cage-displacement limitingmechanism, will next be described. FIG. 3 shows the sprags 11 justassembled between the inner and outer races 3,1. The sprags 11 are incontact with the races 3,1 by the urging force of the ribbon spring 9and are at their normal free positions where they are allowed to movefreely toward either free or locked side, which will be describedsubsequently, depending on the direction of relative rotation betweenthe inner and outer races 3,1. In this case, there are clearances atboth ends of the extension 7d at the engaged parts of the notch 5b andextension 7b as mentioned above. Both cages are therefore allowed tomove relative to each other. When the sprags 11 fall toward the freeside from the above-described positions, the relative movement betweenboth of the cages is limited directly at a position L as indicated inFIG. 4. Therefore, the sprags 11 are prevented from falling too muchtoward the free side. When the sprags 11 fall toward the locked side,the relative movement between both cages is controlled directly at theposition R as shown in FIG. 5. The sprags 11 are therefore preventedfrom falling toward the locked side.

In the first embodiment, the notch 5b is formed in the outer cage 5 andthe extension 7d is provided with the inner cage 7. This constructionmay be reversed. In addition, as illustrated in FIG. 2, the presentinvention may also be applied to an OWC of such a construction that theflange 5a of the outer cage 5 is supported at the part opposite to theengaged part by the stepped portion of the outer race 1 and no flange isprovided with the inner cage 7. Further, needless to say, the engagedpart may be provided at either one of the axial end portions of theouter cage 5.

The second embodiment of this invention will next be described. Althoughthe inner and outer cages 7,5 are in mutual engagement in theaforementioned first embodiment, intermediate members are used in thesecond embodiment.

In FIG. 6, shell-type end bearings 15,17 are used as intermediatemembers in order to limit the relative displacements of the outer andinner cages 5,7. In this embodiment, the outer and inner cages 5,7respectively have at least one axially-extending rectangular extensions5d,7e on their peripheral end surfaces which are located on the sidesopposite to the flanges. The end bearing 17 defines, at locationscorresponding to the extensions 5d,7e, peripherally-extending slots17a,17b in which the extensions 5d,7e are received respectively (see,FIG. 8). The number of such slots must correspond to that of extensions.Since the axial lengths of the extensions 5d,7e are greater than thedepths of the slots 17a,17b of the end bearing 17, the extensions 5d,7eand slots 17a,17b will not be disengaged by vibrations or the like.

Here, reference is made to FIG. 8 which is a fragmentary plan viewcorresponding to FIG. 6. FIG. 8 shows the manner of reception of theextensions 5d,7e in their corresponding slots 17a,17b of the end bearing17. As readily envisaged from the figure, the extensions 5d,7e have thesame radius of curvature as the slots 17a,17b. Each of the engaged partshas a greater clearance in the peripheral direction than in the radialdirection. The clearance in the peripheral direction should bedetermined properly so as to avoid such a situation that the relativedisplacements of the cages 5,7 are limited too much to permit the smoothtilting of the sprags 11.

The operation of the OWC of the second embodiment is similar to that ofthe first embodiment. The relative displacements of both cages 5,7 arelimited as a result that both sides of the extensions 5d,7e arerespectively brought into abutment against both end edges C,D of theslots 17a,17b. Since their displacements are limited like the firstembodiment whenever the sprags 11 fall toward the free side or lockedside, the sprags 11 are prevented from falling unduly. In thisembodiment, there is another advantage that the end bearing 17 isprevented from rotating along with the outer race 1 or inner race 3.FIG. 7 shows a modification of the second embodiment. Rectangularextensions 5e,7f are provided with parts of the flanges 5a,7a of theouter and inner cages 5,7. The extensions 5e,7f are maintained inengagement with their corresponding slots which extend in the peripheraldirection and are formed through the annular flanges 15a,15b maintainedin contact with the inner and outer peripheral surfaces 1a,3a.

The embodiments of this invention have been described in detail. Theabove-described embodiments and their modifications shall however not beconstrued in a manner limiting the present invention. Needless to say,other modifications are feasible. For example, the shapes of thenotches, extensions and slots are substantially rectangular at theengaged part between the outer and inner cages and the engaged partsbetween the outer and inner cages and auxiliary members in theabove-described embodiments. Their shapes are not necessarily requiredto be rectangular.

Having now fully described the invention, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit or scope of the inventionas set forth herein.

We claim:
 1. A one-way clutch with a cage-displacement limitingmechanism, comprising:an outer race having an inner peripheral surface;an inner race having an outer peripheral surface and arrangedconcentrically with the outer race; sprags arranged within an annularspace formed between the outer and inner races and being displaceablebetween first positions, where the sprags are maintained in contact withthe inner and outer peripheral surfaces to transmit a torque, and secondpositions where the sprags are unable to transmit any torque; first andsecond annular cages arranged within the space with a radial intervaltherebetween, holding the sprags in place, and being rotatable relativeto each other between first relative positions, where the sprags arecaused to move to the first positions, and second relative positionswhere the sprags are caused to move to the second positions; a limitingmeans for connecting the cages to each other and for limiting thedegrees of circumferential movements of the cages relative to eachother; and a means for urging the sprags to the first positions, whereineach of the first and second cages has two side surfaces, the limitingmeans comprises a first engagement part formed on one of the sidesurfaces of the first cage and a second engagement part formed on one ofthe side surfaces of the second cage, and the second engagement part isengageable with the first engagement part.
 2. The one-way clutch asclaimed in claim 1, wherein the second cage has, on said one sidesurface, a flange extending toward the first cage and the secondengagement part is formed on the flange.
 3. The one-way clutch asclaimed in claim 1, wherein one of the first and second engagement partsis a notch and the other is an extension extending into the notch. 4.The one-way clutch as claimed in claim 1, wherein the first and secondcages have, on the other side surfaces thereof, annular flangesextending away from the second and first cages respectively, a free edgeof one of the flanges is guided by the inner peripheral surface of theouter race, and the free edge of the other flange is guided by the outerperipheral surface of the inner race.
 5. The one-way clutch as claimedin claim 1, wherein a stepped portion is formed in the inner or outerrace, a flange is formed on the other side surface of the first cageextending in a direction away from the second cage, and a free edgeportion of the flange is received in the stepped portion.
 6. A one-wayclutch with a cage-displacement limiting mechanism, comprising:an outerrace having an inner peripheral surface; an inner race having a outerperipheral surface and arranged concentrically with the outer race;sprags arranged within an annular space formed between the outer andinner races and being displaceable between first positions, where thesprags are maintained in contact with the inner and outer peripheralsurfaces to transmit a torque, and second positions where the sprags areunable to transmit any torque; first and second annular cages arrangedwithin the space with a radial interval therebetween, holding the spragsin place, and being rotatable relative to each other between firstrelative positions, where the sprags are caused to move to the firstpositions, and second relative positions where the sprags are caused tomove to the second positions; a means for urging the sprags to the firstpositions; an end bearing provided between the inner and outer races;and a limiting means provided between the end bearing and the cages forlimiting the degrees of circumferential movements of the cages relativeto each other, wherein the limiting means comprises first engagementparts formed respectively on one side surface of the first and secondcages and second engagement parts formed on the end bearing andengageable respectively with the first engagement parts, and wherein theend bearing has a first flange maintained in contact with the innerperipheral surface of the outer race, a second flange maintained incontact with the outer peripheral surface of the inner race and a partconnecting the first and second flanges to each other, the secondengagement part is a slot formed through the connecting part, and thefirst engagement part is an extension received in the slot.
 7. Theone-way clutch as claimed in claim 6, wherein the length of theextension is greater than the thickness of the end bearing.
 8. Theone-way clutch as claimed in claim 6, wherein the extension hassubstantially a rectangular cross-section, and the clearance between theextension and the edge of the slot is wider in the circumferentialdirection than in the radial direction.